It is known that during certain surgical procedures it is necessary to establish an extracorporeal circulation of the blood of the patient in a circuit that comprises devices suitable to ensure correct treatment of the blood. Such devices comprise at least one reservoir for containing the blood, termed venous blood, that leaves the patient, a pump for conveying the blood in the circuit, a heat exchanger in which the blood encounters a heat exchange fluid that ensures its correct temperature, an oxygenation apparatus meant to transfer oxygen to the blood, and finally a filter that is interposed on the line, known as the arterial blood line, that returns the blood to the patient, with the purpose of retaining any air bubbles that are present in the blood. The described extracorporeal circuit is completed by the presence of a container for the blood collected by salvage from the operating field, know as a cardiotomy reservoir, which is connected to the venous blood reservoir.
In addition to the described devices, in the described circuit there is also often a hemoconcentrator, to which a portion of the blood that flows in the circuit is fed, if required, in order to be concentrated. The hemoconcentrator comprises an enclosure for containing the structure suitable to concentrate the blood. Such structures include a bundle of capillary fibers that are meant to be crossed by the blood and allow ultrafiltered liquid to exit from their walls, consequently concentrating the blood. The conditions of the ultrafiltration depend on the transmembrane pressure, which is the average of the input and output pressures of the blood and can be changed by virtue of devices for throttling the line that conveys the concentrated blood in output.
In the art, the hemoconcentrator is an independent element that is connected to a point of the circuit by a blood supply line and is provided with a line for conveying the concentrated blood in output to the venous blood reservoir, and this fact produces some disadvantageous characteristics that prevent full optimization of the blood treatment conditions.